According to fluid mosaic model (proposed by Singer & Nicolson) plasma membrane is composed of :–

Options

A. Cellulose, hemicellulose
B. Phospholipid and integrated protein
C. Phospholipid, extrinsic protein, intrinsic protein
D. Phospholipid and hemicellulose

Answer

**Step-by-Step Solution:**

1. **Understanding the Fluid Mosaic Model**: The fluid mosaic model, proposed by Singer and Nicolson, describes the structure of the plasma membrane. It emphasizes that the membrane is not a rigid structure but rather a fluid combination of various components.

2. **Components of the Plasma Membrane**: According to this model, the plasma membrane is primarily composed of:
- **Phospholipids**: These molecules form a bilayer, with hydrophilic (water-attracting) heads facing outward and hydrophobic (water-repelling) tails facing inward.
- **Proteins**: There are two types of proteins associated with the membrane:
- **Intrinsic (or Integral) Proteins**: These proteins are embedded within the lipid bilayer and can span across the membrane.
- **Extrinsic (or Peripheral) Proteins**: These proteins are attached to the exterior or interior surfaces of the membrane but do not penetrate the lipid bilayer.

3. **Evaluating the Options**:
- **Option 1**: Cellulose - This is incorrect as cellulose is a component of the cell wall, not the plasma membrane.
- **Option 2**: Phospholipid and integrated protein - This is partially correct but does not mention the extrinsic proteins.
- **Option 3**: Phospholipid, extrinsic protein, and intrinsic protein - This option correctly identifies all the key components of the plasma membrane according to the fluid mosaic model.
- **Option 4**: Phospholipid and hemicellulose - This is incorrect as hemicellulose is also part of the cell wall.

4. **Conclusion**: The correct answer is **Option 3: Phospholipid, extrinsic protein, and intrinsic protein**.

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